using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

using Pgno = System.UInt32;
using i64 = System.Int64;
using u32 = System.UInt32;
using BITVEC_TELEM = System.Byte;

namespace Community.CsharpSqlite
{

  public partial class Sqlite3
  {
    /*
    ** 2008 February 16
    **
    ** The author disclaims copyright to this source code.  In place of
    ** a legal notice, here is a blessing:
    **
    **    May you do good and not evil.
    **    May you find forgiveness for yourself and forgive others.
    **    May you share freely, never taking more than you give.
    **
    *************************************************************************
    ** This file implements an object that represents a fixed-length
    ** bitmap.  Bits are numbered starting with 1.
    **
    ** A bitmap is used to record which pages of a database file have been
    ** journalled during a transaction, or which pages have the "dont-write"
    ** property.  Usually only a few pages are meet either condition.
    ** So the bitmap is usually sparse and has low cardinality.
    ** But sometimes (for example when during a DROP of a large table) most
    ** or all of the pages in a database can get journalled.  In those cases,
    ** the bitmap becomes dense with high cardinality.  The algorithm needs
    ** to handle both cases well.
    **
    ** The size of the bitmap is fixed when the object is created.
    **
    ** All bits are clear when the bitmap is created.  Individual bits
    ** may be set or cleared one at a time.
    **
    ** Test operations are about 100 times more common that set operations.
    ** Clear operations are exceedingly rare.  There are usually between
    ** 5 and 500 set operations per Bitvec object, though the number of sets can
    ** sometimes grow into tens of thousands or larger.  The size of the
    ** Bitvec object is the number of pages in the database file at the
    ** start of a transaction, and is thus usually less than a few thousand,
    ** but can be as large as 2 billion for a really big database.
    *************************************************************************
    **  Included in SQLite3 port to C#-SQLite;  2008 Noah B Hart
    **  C#-SQLite is an independent reimplementation of the SQLite software library
    **
    **  SQLITE_SOURCE_ID: 2009-12-07 16:39:13 1ed88e9d01e9eda5cbc622e7614277f29bcc551c
    **
    **  $Header: Community.CsharpSqlite/src/bitvec_c.cs,v bcbd36f24b23 2010/02/18 17:35:24 Noah $
    *************************************************************************
    */
    //#include "sqliteInt.h"

    /* Size of the Bitvec structure in bytes. */
    static int BITVEC_SZ = IntPtr.Size * 128;//(sizeof(void*)*128)  /* 512 on 32bit.  1024 on 64bit */


    /* Round the union size down to the nearest pointer boundary, since that's how
    ** it will be aligned within the Bitvec struct. */
    //#define BITVEC_USIZE     (((BITVEC_SZ-(3*sizeof(u32)))/sizeof(Bitvec*))*sizeof(Bitvec*))
    static int BITVEC_USIZE = ( ( ( BITVEC_SZ - ( 3 * sizeof( u32 ) ) ) / 4 ) * 4 );

    /* Type of the array "element" for the bitmap representation.
    ** Should be a power of 2, and ideally, evenly divide into BITVEC_USIZE.
    ** Setting this to the "natural word" size of your CPU may improve
    ** performance. */
    //#define BITVEC_TELEM     u8
    //using BITVEC_TELEM     = System.Byte;

    /* Size, in bits, of the bitmap element. */
    //#define BITVEC_SZELEM    8
    const int BITVEC_SZELEM = 8;

    /* Number of elements in a bitmap array. */
    //#define BITVEC_NELEM     (BITVEC_USIZE/sizeof(BITVEC_TELEM))
    static int BITVEC_NELEM = (int)( BITVEC_USIZE / sizeof( BITVEC_TELEM ) );

    /* Number of bits in the bitmap array. */
    //#define BITVEC_NBIT      (BITVEC_NELEM*BITVEC_SZELEM)
    static int BITVEC_NBIT = ( BITVEC_NELEM * BITVEC_SZELEM );

    /* Number of u32 values in hash table. */
    //#define BITVEC_NINT      (BITVEC_USIZE/sizeof(u32))
    static u32 BITVEC_NINT = (u32)( BITVEC_USIZE / sizeof( u32 ) );

    /* Maximum number of entries in hash table before
    ** sub-dividing and re-hashing. */
    //#define BITVEC_MXHASH    (BITVEC_NINT/2)
    static int BITVEC_MXHASH = (int)( BITVEC_NINT / 2 );

    /* Hashing function for the aHash representation.
    ** Empirical testing showed that the *37 multiplier
    ** (an arbitrary prime)in the hash function provided
    ** no fewer collisions than the no-op *1. */
    //#define BITVEC_HASH(X)   (((X)*1)%BITVEC_NINT)
    static u32 BITVEC_HASH( u32 X ) { return (u32)( ( ( X ) * 1 ) % BITVEC_NINT ); }

    static int BITVEC_NPTR = (int)( BITVEC_USIZE / 4 );//sizeof(Bitvec *));


    /*
    ** A bitmap is an instance of the following structure.
    **
    ** This bitmap records the existence of zero or more bits
    ** with values between 1 and iSize, inclusive.
    **
    ** There are three possible representations of the bitmap.
    ** If iSize<=BITVEC_NBIT, then Bitvec.u.aBitmap[] is a straight
    ** bitmap.  The least significant bit is bit 1.
    **
    ** If iSize>BITVEC_NBIT and iDivisor==0 then Bitvec.u.aHash[] is
    ** a hash table that will hold up to BITVEC_MXHASH distinct values.
    **
    ** Otherwise, the value i is redirected into one of BITVEC_NPTR
    ** sub-bitmaps pointed to by Bitvec.u.apSub[].  Each subbitmap
    ** handles up to iDivisor separate values of i.  apSub[0] holds
    ** values between 1 and iDivisor.  apSub[1] holds values between
    ** iDivisor+1 and 2*iDivisor.  apSub[N] holds values between
    ** N*iDivisor+1 and (N+1)*iDivisor.  Each subbitmap is normalized
    ** to hold deal with values between 1 and iDivisor.
    */
    public class _u
    {
      public BITVEC_TELEM[] aBitmap = new byte[BITVEC_NELEM];   /* Bitmap representation */
      public u32[] aHash = new u32[BITVEC_NINT];        /* Hash table representation */
      public Bitvec[] apSub = new Bitvec[BITVEC_NPTR];  /* Recursive representation */
    }
    public class Bitvec
    {
      public u32 iSize;     /* Maximum bit index.  Max iSize is 4,294,967,296. */
      public u32 nSet;      /* Number of bits that are set - only valid for aHash
      ** element.  Max is BITVEC_NINT.  For BITVEC_SZ of 512,
      ** this would be 125. */
      public u32 iDivisor;  /* Number of bits handled by each apSub[] entry. */
      /* Should >=0 for apSub element. */
      /* Max iDivisor is max(u32) / BITVEC_NPTR + 1.  */
      /* For a BITVEC_SZ of 512, this would be 34,359,739. */
      public _u u = new _u();

      public static implicit operator bool( Bitvec b )
      {
        return ( b != null );
      }
    };

    /*
    ** Create a new bitmap object able to handle bits between 0 and iSize,
    ** inclusive.  Return a pointer to the new object.  Return NULL if
    ** malloc fails.
    */
    static Bitvec sqlite3BitvecCreate( u32 iSize )
    {
      Bitvec p;
      //Debug.Assert( sizeof(p)==BITVEC_SZ );
      p = new Bitvec();//sqlite3MallocZero( sizeof(p) );
      if ( p != null )
      {
        p.iSize = iSize;
      }
      return p;
    }

    /*
    ** Check to see if the i-th bit is set.  Return true or false.
    ** If p is NULL (if the bitmap has not been created) or if
    ** i is out of range, then return false.
    */
    static int sqlite3BitvecTest( Bitvec p, u32 i )
    {
      if ( p == null || i == 0 ) return 0;
      if ( i > p.iSize ) return 0;
      i--;
      while ( p.iDivisor != 0 )
      {
        u32 bin = i / p.iDivisor;
        i = i % p.iDivisor;
        p = p.u.apSub[bin];
        if ( null == p )
        {
          return 0;
        }
      }
      if ( p.iSize <= BITVEC_NBIT )
      {
        return ( ( p.u.aBitmap[i / BITVEC_SZELEM] & ( 1 << (int)( i & ( BITVEC_SZELEM - 1 ) ) ) ) != 0 ) ? 1 : 0;
      }
      else
      {
        u32 h = BITVEC_HASH( i++ );
        while ( p.u.aHash[h] != 0 )
        {
          if ( p.u.aHash[h] == i ) return 1;
          h = ( h + 1 ) % BITVEC_NINT;
        }
        return 0;
      }
    }

    /*
    ** Set the i-th bit.  Return 0 on success and an error code if
    ** anything goes wrong.
    **
    ** This routine might cause sub-bitmaps to be allocated.  Failing
    ** to get the memory needed to hold the sub-bitmap is the only
    ** that can go wrong with an insert, assuming p and i are valid.
    **
    ** The calling function must ensure that p is a valid Bitvec object
    ** and that the value for "i" is within range of the Bitvec object.
    ** Otherwise the behavior is undefined.
    */
    static int sqlite3BitvecSet( Bitvec p, u32 i )
    {
      u32 h;
      if ( p == null ) return SQLITE_OK;
      Debug.Assert( i > 0 );
      Debug.Assert( i <= p.iSize );
      i--;
      while ( ( p.iSize > BITVEC_NBIT ) && p.iDivisor != 0 )
      {
        u32 bin = i / p.iDivisor;
        i = i % p.iDivisor;
        if ( p.u.apSub[bin] == null )
        {
          p.u.apSub[bin] = sqlite3BitvecCreate( p.iDivisor );
          if ( p.u.apSub[bin] == null ) return SQLITE_NOMEM;
        }
        p = p.u.apSub[bin];
      }
      if ( p.iSize <= BITVEC_NBIT )
      {
        p.u.aBitmap[i / BITVEC_SZELEM] |= (byte)( 1 << (int)( i & ( BITVEC_SZELEM - 1 ) ) );
        return SQLITE_OK;
      }
      h = BITVEC_HASH( i++ );
      /* if there wasn't a hash collision, and this doesn't */
      /* completely fill the hash, then just add it without */
      /* worring about sub-dividing and re-hashing. */
      if ( 0 == p.u.aHash[h] )
      {
        if ( p.nSet < ( BITVEC_NINT - 1 ) )
        {
          goto bitvec_set_end;
        }
        else
        {
          goto bitvec_set_rehash;
        }
      }
      /* there was a collision, check to see if it's already */
      /* in hash, if not, try to find a spot for it */
      do
      {
        if ( p.u.aHash[h] == i ) return SQLITE_OK;
        h++;
        if ( h >= BITVEC_NINT ) h = 0;
      } while ( p.u.aHash[h] != 0 );
    /* we didn't find it in the hash.  h points to the first */
    /* available free spot. check to see if this is going to */
    /* make our hash too "full".  */
    bitvec_set_rehash:
      if ( p.nSet >= BITVEC_MXHASH )
      {
        u32 j;
        int rc;
        u32[] aiValues = new u32[BITVEC_NINT];// = sqlite3StackAllocRaw(0, sizeof(p->u.aHash));
        if ( aiValues == null )
        {
          return SQLITE_NOMEM;
        }
        else
        {

          Buffer.BlockCopy( p.u.aHash, 0, aiValues, 0, aiValues.Length * ( sizeof( u32 ) ) );// memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
          p.u.apSub = new Bitvec[BITVEC_NPTR];//memset(p->u.apSub, 0, sizeof(p->u.apSub));
          p.iDivisor = (u32)( ( p.iSize + BITVEC_NPTR - 1 ) / BITVEC_NPTR );
          rc = sqlite3BitvecSet( p, i );
          for ( j = 0; j < BITVEC_NINT; j++ )
          {
            if ( aiValues[j] != 0 ) rc |= sqlite3BitvecSet( p, aiValues[j] );
          }
          //sqlite3StackFree( null, aiValues );
          return rc;
        }
      }
    bitvec_set_end:
      p.nSet++;
      p.u.aHash[h] = i;
      return SQLITE_OK;
    }

    /*
    ** Clear the i-th bit.
    **
    ** pBuf must be a pointer to at least BITVEC_SZ bytes of temporary storage
    ** that BitvecClear can use to rebuilt its hash table.
    */
    static void sqlite3BitvecClear( Bitvec p, u32 i, u32[] pBuf )
    {
      if ( p == null ) return;
      Debug.Assert( i > 0 );
      i--;
      while ( p.iDivisor != 0 )
      {
        u32 bin = i / p.iDivisor;
        i = i % p.iDivisor;
        p = p.u.apSub[bin];
        if ( null == p )
        {
          return;
        }
      }
      if ( p.iSize <= BITVEC_NBIT )
      {
        p.u.aBitmap[i / BITVEC_SZELEM] &= (byte)~( ( 1 << (int)( i & ( BITVEC_SZELEM - 1 ) ) ) );
      }
      else
      {
        u32 j;
        u32[] aiValues = pBuf;
        Array.Copy( p.u.aHash, aiValues, p.u.aHash.Length );//memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
        p.u.aHash = new u32[aiValues.Length];// memset(p->u.aHash, 0, sizeof(p->u.aHash));
        p.nSet = 0;
        for ( j = 0; j < BITVEC_NINT; j++ )
        {
          if ( aiValues[j] != 0 && aiValues[j] != ( i + 1 ) )
          {
            u32 h = BITVEC_HASH( aiValues[j] - 1 );
            p.nSet++;
            while ( p.u.aHash[h] != 0 )
            {
              h++;
              if ( h >= BITVEC_NINT ) h = 0;
            }
            p.u.aHash[h] = aiValues[j];
          }
        }
      }
    }

    /*
    ** Destroy a bitmap object.  Reclaim all memory used.
    */
    static void sqlite3BitvecDestroy( ref Bitvec p )
    {
      if ( p == null ) return;
      if ( p.iDivisor != 0 )
      {
        u32 i;
        for ( i = 0; i < BITVEC_NPTR; i++ )
        {
          sqlite3BitvecDestroy( ref p.u.apSub[i] );
        }
      }
      //sqlite3_free( ref p );
    }

    /*
    ** Return the value of the iSize parameter specified when Bitvec *p
    ** was created.
    */
    static u32 sqlite3BitvecSize( Bitvec p )
    {
      return p.iSize;
    }

#if !SQLITE_OMIT_BUILTIN_TEST
    /*
** Let V[] be an array of unsigned characters sufficient to hold
** up to N bits.  Let I be an integer between 0 and N.  0<=I<N.
** Then the following macros can be used to set, clear, or test
** individual bits within V.
*/
    //#define SETBIT(V,I)      V[I>>3] |= (1<<(I&7))
    static void SETBIT( byte[] V, int I ) { V[I >> 3] |= (byte)( 1 << ( I & 7 ) ); }

    //#define CLEARBIT(V,I)    V[I>>3] &= ~(1<<(I&7))
    static void CLEARBIT( byte[] V, int I ) { V[I >> 3] &= (byte)~( 1 << ( I & 7 ) ); }

    //#define TESTBIT(V,I)     (V[I>>3]&(1<<(I&7)))!=0
    static int TESTBIT( byte[] V, int I ) { return ( V[I >> 3] & ( 1 << ( I & 7 ) ) ) != 0 ? 1 : 0; }

    /*
    ** This routine runs an extensive test of the Bitvec code.
    **
    ** The input is an array of integers that acts as a program
    ** to test the Bitvec.  The integers are opcodes followed
    ** by 0, 1, or 3 operands, depending on the opcode.  Another
    ** opcode follows immediately after the last operand.
    **
    ** There are 6 opcodes numbered from 0 through 5.  0 is the
    ** "halt" opcode and causes the test to end.
    **
    **    0          Halt and return the number of errors
    **    1 N S X    Set N bits beginning with S and incrementing by X
    **    2 N S X    Clear N bits beginning with S and incrementing by X
    **    3 N        Set N randomly chosen bits
    **    4 N        Clear N randomly chosen bits
    **    5 N S X    Set N bits from S increment X in array only, not in bitvec
    **
    ** The opcodes 1 through 4 perform set and clear operations are performed
    ** on both a Bitvec object and on a linear array of bits obtained from malloc.
    ** Opcode 5 works on the linear array only, not on the Bitvec.
    ** Opcode 5 is used to deliberately induce a fault in order to
    ** confirm that error detection works.
    **
    ** At the conclusion of the test the linear array is compared
    ** against the Bitvec object.  If there are any differences,
    ** an error is returned.  If they are the same, zero is returned.
    **
    ** If a memory allocation error occurs, return -1.
    */
    static int sqlite3BitvecBuiltinTest( u32 sz, int[] aOp )
    {
      Bitvec pBitvec = null;
      byte[] pV = null;
      int rc = -1;
      int i, nx, pc, op;
      u32[] pTmpSpace;

      /* Allocate the Bitvec to be tested and a linear array of
      ** bits to act as the reference */
      pBitvec = sqlite3BitvecCreate( sz );
      pV = sqlite3_malloc( (int)( sz + 7 ) / 8 + 1 );
      pTmpSpace = new u32[BITVEC_SZ];// sqlite3_malloc( BITVEC_SZ );
      if ( pBitvec == null || pV == null || pTmpSpace == null ) goto bitvec_end;
      Array.Clear( pV, 0, (int)( sz + 7 ) / 8 + 1 );// memset( pV, 0, ( sz + 7 ) / 8 + 1 );

      /* NULL pBitvec tests */
      sqlite3BitvecSet( null, (u32)1 );
      sqlite3BitvecClear( null, 1, pTmpSpace );

      /* Run the program */
      pc = 0;
      while ( ( op = aOp[pc] ) != 0 )
      {
        switch ( op )
        {
          case 1:
          case 2:
          case 5:
            {
              nx = 4;
              i = aOp[pc + 2] - 1;
              aOp[pc + 2] += aOp[pc + 3];
              break;
            }
          case 3:
          case 4:
          default:
            {
              nx = 2;
              i64 i64Temp = 0;
              sqlite3_randomness( sizeof( i64 ), ref i64Temp );
              i = (int)i64Temp;
              break;
            }
        }
        if ( ( --aOp[pc + 1] ) > 0 ) nx = 0;
        pc += nx;
        i = (int)( ( i & 0x7fffffff ) % sz );
        if ( ( op & 1 ) != 0 )
        {
          SETBIT( pV, ( i + 1 ) );
          if ( op != 5 )
          {
            if ( sqlite3BitvecSet( pBitvec, (u32)i + 1 ) != 0 ) goto bitvec_end;
          }
        }
        else
        {
          CLEARBIT( pV, ( i + 1 ) );
          sqlite3BitvecClear( pBitvec, (u32)i + 1, pTmpSpace );
        }
      }

      /* Test to make sure the linear array exactly matches the
      ** Bitvec object.  Start with the assumption that they do
      ** match (rc==0).  Change rc to non-zero if a discrepancy
      ** is found.
      */
      rc = sqlite3BitvecTest( null, 0 ) + sqlite3BitvecTest( pBitvec, sz + 1 )
      + sqlite3BitvecTest( pBitvec, 0 )
      + (int)( sqlite3BitvecSize( pBitvec ) - sz );
      for ( i = 1; i <= sz; i++ )
      {
        if ( ( TESTBIT( pV, i ) ) != sqlite3BitvecTest( pBitvec, (u32)i ) )
        {
          rc = i;
          break;
        }
      }

          /* Free allocated structure */
    bitvec_end:
      //sqlite3_free( ref pTmpSpace );
      //sqlite3_free( ref pV );
      sqlite3BitvecDestroy( ref pBitvec );
      return rc;
    }
#endif //* SQLITE_OMIT_BUILTIN_TEST */
  }
}
